The present invention relates to optical display calibration methods and apparatus. More particularly, the present invention relates to novel display calibration test patterns and methods of use. Applications may be applied to displays of any type of media, such as computer animated media.
Throughout the years, movie makers have often tried to tell stories involving make-believe creatures, far away places, and fantastic things. To do so, they have often relied on animation techniques to bring the make-believe to “life.” Two of the major paths in animation have traditionally included, drawing-based animation techniques and stop motion animation techniques.
Drawing-based animation techniques were refined in the twentieth century, by movie makers such as Walt Disney and used in movies such as “Snow White and the Seven Dwarfs” (1937) and “Fantasia” (1940). This animation technique typically required artists to hand-draw (or paint) animated images onto a transparent media or cells. After painting, each cell would then be captured or recorded onto film as one or more frames in a movie.
Stop motion-based animation techniques typically required the construction of miniature sets, props, and characters. The filmmakers would construct the sets, add props, and position the miniature characters in a pose. After the animator was happy with how everything was arranged, one or more frames of film would be taken of that specific arrangement. Stop motion animation techniques were developed by movie makers such as Willis O'Brien for movies such as “King Kong” (1933). Subsequently, these techniques were refined by animators such as Ray Harryhausen for movies including “Mighty Joe Young” (1948) and Clash Of The Titans (1981).
With the wide-spread availability of computers in the later part of the twentieth century, animators began to rely upon computers to assist in the animation process. This included using computers to facilitate drawing-based animation, for example, by painting images, by generating in-between images (“tweening”), and the like. This also included using computers to augment stop motion animation techniques. For example, physical models could be represented by virtual models in computer memory, and manipulated.
One of the pioneering companies in the computer-aided animation (CA) industry was Pixar. Pixar is more widely known as Pixar Animation Studios, the creators of animated features such as “Toy Story” (1995) and “Toy Story 2” (1999), “A Bugs Life” (1998), “Monsters, Inc.” (2001), “Finding Nemo” (2003), “The Incredibles” (2004), and others. In addition to creating animated features, Pixar developed computing platforms specially designed for CA, and CA software now known as RenderMan®. RenderMan® was particularly well received in the animation industry and recognized with two Academy Awards®. The RenderMan® software included a “rendering engine” that “rendered” or converted geometric and/or mathematical descriptions of objects into a two dimensional image. Images are then recorded to a media such as film, DVD, or the like, for later viewing.
To display the rendered and recorded images to viewers (e.g. audience, users) in a manner contemplated by the director, display devices need to be properly tuned or calibrated. Some types of calibration include black level adjustment, white level adjustment, gamma correction, contrast adjustment and the like. In the past, methods for optically calibrating displays have typically relied upon static calibration images. Specifically, a calibration image would be displayed on a display device, and based upon how the image appeared on the display device, a user would adjust the brightness, contrast, and the like of the display device. Alternatively, a user would adjust a display driver until the calibration image appeared “correct” to the viewer.
The inventor of the present invention has determined that the ability of users to correctly judge or determine when the calibration image appeared “correct” was often difficult, in part, because of the way humans detect changes in luminance values. More specifically, the inventor realized that with static images, it is difficult for a human to determine whether two similar shades of gray, for example, appear different when displayed.
The inventor also realized that conventional DVD players are thought by some practitioners to be unable to reliably display variations in gray scale of less than approximately 4%. Because of this low accuracy, it has previously been difficult to readily calibrate displays driven by such DVD players, or the like, to a high degree of accuracy.
Additionally, the inventor of the present invention has also determined that although some dedicated display calibration software may have been available, such software was not widely used. One reason was that they were typically stand-alone software packages that a user would have to specifically purchase. Another reason was that they included a number of separate tests for each parameter to be adjusted and requires a user to run a large number of individual tests to calibrate a display. This was also very burdensome, thus consumers were not performing such calibrations. For these reasons, and others, such packages do not appear to be widely used by consumers.
Accordingly, what is desired are improved methods for presenting calibration data to users to facilitate the calibration of displays devices.